I2 + Ag = AgI

I_2 iodine + Ag silver ⟶ AgI silver(I) iodide

Balance the chemical equation algebraically: I_2 + Ag ⟶ AgI Add stoichiometric coefficients, c_i, to the reactants and products: c_1 I_2 + c_2 Ag ⟶ c_3 AgI Set the number of atoms in the reactants equal to the number of atoms in the products for I and Ag: I: | 2 c_1 = c_3 Ag: | c_2 = c_3 Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 2 c_3 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | I_2 + 2 Ag ⟶ 2 AgI

+ ⟶

iodine + silver ⟶ silver(I) iodide

| iodine | silver | silver(I) iodide molecular enthalpy | 0 kJ/mol | 0 kJ/mol | -61.8 kJ/mol total enthalpy | 0 kJ/mol | 0 kJ/mol | -123.6 kJ/mol | H_initial = 0 kJ/mol | | H_final = -123.6 kJ/mol ΔH_rxn^0 | -123.6 kJ/mol - 0 kJ/mol = -123.6 kJ/mol (exothermic) | |

| iodine | silver | silver(I) iodide molecular entropy | 116.1 J/(mol K) | 42.6 J/(mol K) | 115.5 J/(mol K) total entropy | 116.1 J/(mol K) | 85.2 J/(mol K) | 231 J/(mol K) | S_initial = 201.3 J/(mol K) | | S_final = 231 J/(mol K) ΔS_rxn^0 | 231 J/(mol K) - 201.3 J/(mol K) = 29.66 J/(mol K) (endoentropic) | |

Construct the equilibrium constant, K, expression for: I_2 + Ag ⟶ AgI Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the activity expression for each chemical species. • Use the activity expressions to build the equilibrium constant expression. Write the balanced chemical equation: I_2 + 2 Ag ⟶ 2 AgI Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i I_2 | 1 | -1 Ag | 2 | -2 AgI | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression I_2 | 1 | -1 | ([I2])^(-1) Ag | 2 | -2 | ([Ag])^(-2) AgI | 2 | 2 | ([AgI])^2 The equilibrium constant symbol in the concentration basis is: K_c Mulitply the activity expressions to arrive at the K_c expression: Answer: | | K_c = ([I2])^(-1) ([Ag])^(-2) ([AgI])^2 = ([AgI])^2/([I2] ([Ag])^2)

Construct the rate of reaction expression for: I_2 + Ag ⟶ AgI Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the rate term for each chemical species. • Write the rate of reaction expression. Write the balanced chemical equation: I_2 + 2 Ag ⟶ 2 AgI Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i I_2 | 1 | -1 Ag | 2 | -2 AgI | 2 | 2 The rate term for each chemical species, B_i, is 1/ν_i(Δ[B_i])/(Δt) where [B_i] is the amount concentration and t is time: chemical species | c_i | ν_i | rate term I_2 | 1 | -1 | -(Δ[I2])/(Δt) Ag | 2 | -2 | -1/2 (Δ[Ag])/(Δt) AgI | 2 | 2 | 1/2 (Δ[AgI])/(Δt) (for infinitesimal rate of change, replace Δ with d) Set the rate terms equal to each other to arrive at the rate expression: Answer: | | rate = -(Δ[I2])/(Δt) = -1/2 (Δ[Ag])/(Δt) = 1/2 (Δ[AgI])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iodine | silver | silver(I) iodide formula | I_2 | Ag | AgI name | iodine | silver | silver(I) iodide IUPAC name | molecular iodine | silver | silver iodide

| iodine | silver | silver(I) iodide molar mass | 253.80894 g/mol | 107.8682 g/mol | 234.7727 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) melting point | 113 °C | 960 °C | 557 °C boiling point | 184 °C | 2212 °C | 1506 °C density | 4.94 g/cm^3 | 10.49 g/cm^3 | 5.68 g/cm^3 solubility in water | | insoluble | slightly soluble dynamic viscosity | 0.00227 Pa s (at 116 °C) | |